1. Field of the Invention
The present invention relates generally to establishing a junction for the two ends of glass fibers across which light signals can be efficiently transmitted, and, more particularly, to an optical fiber termination of simplified construction not requiring the use of adhesive materials for securing the fiber within the termination parts.
2. Description of Related Art
A frequent requirement in optical fiber equipment is to be able to interconnect two ends of a fiber that has been broken or the ends of two separate fibers, in such a way as to enable transmission of an optical signal along the fibers and across the junction. For an interconnection to be satisfactory, it must be able to transmit substantially the full optical signal not losing more than a few percent as the signal passes across the junction.
One effective optical fiber termination is disclosed in U.S. Pat. No. 4,483,584 to John Gresty assigned to the same assignee as the present application. The patented device has the ends of the two fibers to be interconnected faced off to form flat smooth surfaces precisely 90 degrees to the fiber longitudinal axis. Each of the fiber end portions are mounted within separate sets of three cylindrical pins holding the fiber within the interstices of the pins. The three pins with included fiber are, in turn, received within the opposite ends of a cylindrical alignment tube thereby effecting collimation of the fibers and locating the ends in a required slightly spaced, end facing relation. Such a connector, although highly effective, is complex and relatively expensive to manufacture as well as somewhat difficult to effect a fiber optic termination under field conditions.
U.S. Pat. No. 4,290,667, OPTICAL FIBER TERMINATIONS AND CONNECTIONS by Mark Chown discloses a termination technique in which each fiber has its end portion received within a capillary tube and with a faced-off fiber end located at the focal point of a lens. Two such fiber and lens devices are located at opposite ends of an alignment tube to complete the terminus. The patent also discloses other versions in which the optical fiber is clad within a ball lens, and in yet another form the fiber is located within a ferrule having a central recess for receiving a ball lens therein. An adhesive material such as an epoxy is used to match the end of the lens with the fiber.
In U.S. patent application No. 07/524,733, OPTICAL FIBER TERMINATION, by Alex Wasserman, assigned to the same assignee as the present application (now U.S. Pat. No. 5,097,524), a termination means is shown in which the bare glass end portion of an optical fiber is received in an opening within a ferrule end wall and secured therein by a first epoxy material. The outer face of the ferrule end wall is faced-off and substantially coterminus with the end of the fiber. An expanding lens is adhered to the outer surface of the ferrule end wall, and to the end of the faced-off fiber as well, by means of a second epoxy which has optical characteristics closely matching that of the glass portion of the fiber as well as the lens.
It is, therefore, a desideratum to provide an optical fiber termination that is reliable and of simplified construction. Also, since there are many environments in which epoxys cannot be used, or in which it is advisable not to use them, it is further desirable that termination be achieved without epoxy or other adhesive materials. For example, many epoxys require overnight curing which may not be feasible at all as well as being time consuming. On the other hand, so-called "fast curing" epoxys (e.g. 2-3 minutes) have been found to frequently crack the fiber.